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<div class="SECT1"><h1 class="SECT1"><a name="TUTORIAL-UPDATE">2.8. 更新</a></h1><a name="AEN900"></a>
<p>你可以用 <tt class="COMMAND">UPDATE</tt> 命令更新现有的行。假设你发现所有 11 月 28 日的温度计数都低了两度，那么你就可以用下面的方式更新数据：</p>
<pre class="PROGRAMLISTING">UPDATE weather
    SET temp_hi = temp_hi - 2,  temp_lo = temp_lo - 2
    WHERE date &gt; '1994-11-28';</pre>
<p>看看数据的新状态：</p>
<pre class="PROGRAMLISTING">SELECT * FROM weather;

     city      | temp_lo | temp_hi | prcp |    date
---------------+---------+---------+------+------------
 San Francisco |      46 |      50 | 0.25 | 1994-11-27
 San Francisco |      41 |      55 |    0 | 1994-11-29
 Hayward       |      35 |      52 |      | 1994-11-29
(3 rows)</pre>
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